Author
 |
Boyer, Douglas |
|
Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/15/2007 Publication Date: 1/9/2008 Citation: Boyer, D.G. 2008. Assessment of a Sinkhole Filter for Removing Agricultural Contaminants. Journal of Soil and Water Conservation. 63(1):47-52. Interpretive Summary: The impact on water quality by agricultural activity in karst terrain is an important consideration for resource management within the Appalachian Region. Three USDA/NRCS-designed sinkhole filters for removing contaminants from manure-impacted infiltrating water were assessed for removal efficiency of fecal bacteria and nitrate. One sinkhole filter was located in a pasture down slope from a barnyard and milk house. The other two sinkhole filters were constructed in large pasture sinkholes. Fecal coliform bacteria concentrations were reduced by 85 to 96 percent after sinkhole filter installation at two of the locations. Mean nitrate concentrations increased from 2.0 mg N L-1 to 4.6 mg N L-1 and from 5.5 mg N L-1 to 12.9 mg N L-1 at the dairy and pasture sites, respectively. We expect that the sinkhole filters filtered out sediment and associated contaminant, such as fecal coliform bacteria, but had no filtering effect on solutes like nitrate. Nitrate concentrations might have increased because of nitrification in the filter media between runoff events. The sinkhole filter appears to be an effective management tool, along with responsible land management, in order to reduce inputs of pathogens to karst groundwater aquifers. Technical Abstract: The impact on water quality by agricultural activity in karst terrain is an important consideration for resource management within the Appalachian Region. Karst areas comprise about 18 percent of the Region's land area. An estimated one-third of the Region's farms, cattle, and agricultural market value are on karst terrain. Three USDA/NRCS-designed sinkhole filters for removing contaminants from manure-impacted infiltrating water were assessed for removal efficiency of indicator bacteria and nitrate. One sinkhole filter was located in a pasture down slope from a barnyard and milk house. The other two sinkhole filters were constructed in large pasture sinkholes; one rotationally grazed and one continuously grazed by beef cattle. Geometric mean fecal coliform bacteria concentrations were reduced by 85 to 95 percent after sinkhole filter installation at two of the locations. Mean nitrate concentrations increased from 2.0 mg N L-1 to 4.6 mg N L-1 and from 5.5 mg N L-1 to 12.9 mg N L-1 at the dairy and rotationally grazed pasture sites, respectively. The sinkhole filters were designed to filter water without significantly delaying water infiltration and causing sinkhole flooding. We expect that the sinkhole filters filtered out sediment and associated contaminant, such as fecal coliform bacteria, but had no filtering effect on solutes like nitrate. Nitrate concentrations might have increased because of nitrification in the filter media between runoff events. The sinkhole filter appears to be an effective management tool, along with responsible land management, in order to reduce inputs of pathogens to karst groundwater aquifers. |
